Reviews the REA model method for designing AIS.
What is an REA model?
REA (Resources, Agents, Events) a modeling framework and ontology for business systems. REA is the only business modeling method known today that captures the cause-and-effect relationships between business transactions.
The REA data model prescribes a basic pattern for how the three types of entities (resources, events, and agents) should relate to one another.
Rule 1: Each event is linked to at least one resource that it affects.
Rule 2: Each event is linked to at least one other event.
Rule 3: Each event is linked to at least two agents.
How is the REA model of benefit to AIS designers and developers?
ENTITY-RELATIONSHIP MODEL
This a standard way of data modeling, where the entities and relationships are determined through systems analysis. The accounting entities that make up these systems are: Resources: Items owned by the company Events: The actions that happen with the resources Agents: The people or organizations which participate in the events.
Here's an example of an entity-relationship model involving Toyota dealerships in Atlanta, GA: ER_&_EER
CARDINALITIES:
are used to define how the entities participate in the relationship. These are determined by one or many entities (1 or N respectively) participate in one or many relationships.
A one-to-one (1:1) relationship is when at most one instance of a entity A is associated with one instance of entity B. For example, "employees in the company are each assigned their own office. For each employee there exists a unique office and for each office there exists a unique employee.
A one-to-many (1:N) relationships is when for one instance of entity A, there are zero, one, or many instances of entity B, but for one instance of entity B, there is only one instance of entity A. An example of a 1:N relationships is: a department has many employees; each employee is assigned to one department.
A many-to-many (M:N) relationship, sometimes called non-specific, is when for one instance of entity A, there are zero, one, or many instances of entity B and for one instance of entity B there are zero, one, or many instances of entity A. An example is: employees can be assigned to no more than two projects at the same time; projects must have assigned at least three employees.
(1, 1) One to one-An employee can only work in one department. (1, N) One to many--An employee can work on many projects. (N, 1) Many to one--Many employees can attend one training session. (N, N) Many to many--Many payroll runs may have many employees.
Mapping the REA model to a Relational Database (discuss the steps):
1. Create a separate relational table for each entity.
2. Determine the primary key for each of the relations.
- This key must uniquely identify any row within the table.
3. Determine the attributes for each of the entities.
4. Implement the relationships among the entities.
- This is done by ensuring that the primary key is an attribute in every table with which it has a relationship.
5. Determine the attributes, if any, for each of the relationship tables.
REA Model:
Reviews the REA model method for designing AIS.What is an REA model?
REA (Resources, Agents, Events) a modeling framework and ontology for business systems. REA is the only business modeling method known today that captures the cause-and-effect relationships between business transactions.
The REA data model prescribes a basic pattern for how the three types of entities (resources, events, and agents) should relate to one another.
How is the REA model of benefit to AIS designers and developers?
Need Help Understanding REA Models? Visit http://reatechnology.com/what-is-rea.html
ENTITY-RELATIONSHIP MODEL
This a standard way of data modeling, where the entities and relationships are determined through systems analysis. The accounting entities that make up these systems are:
Resources: Items owned by the company
Events: The actions that happen with the resources
Agents: The people or organizations which participate in the events.
Here's an example of an entity-relationship model involving Toyota dealerships in Atlanta, GA:
ER_&_EER
CARDINALITIES:
are used to define how the entities participate in the relationship. These are determined by one or many entities (1 or N respectively) participate in one or many relationships.
A one-to-one (1:1) relationship is when at most one instance of a entity A is associated with one instance of entity B. For example, "employees in the company are each assigned their own office. For each employee there exists a unique office and for each office there exists a unique employee.
A one-to-many (1:N) relationships is when for one instance of entity A, there are zero, one, or many instances of entity B, but for one instance of entity B, there is only one instance of entity A. An example of a 1:N relationships is: a department has many employees; each employee is assigned to one department.
A many-to-many (M:N) relationship, sometimes called non-specific, is when for one instance of entity A, there are zero, one, or many instances of entity B and for one instance of entity B there are zero, one, or many instances of entity A. An example is: employees can be assigned to no more than two projects at the same time; projects must have assigned at least three employees.
(1, 1) One to one-An employee can only work in one department.
(1, N) One to many--An employee can work on many projects.
(N, 1) Many to one--Many employees can attend one training session.
(N, N) Many to many--Many payroll runs may have many employees.
Mapping the REA model to a Relational Database (discuss the steps):
1. Create a separate relational table for each entity.2. Determine the primary key for each of the relations.
- This key must uniquely identify any row within the table.
3. Determine the attributes for each of the entities.
4. Implement the relationships among the entities.
- This is done by ensuring that the primary key is an attribute in every table with which it has a relationship.
5. Determine the attributes, if any, for each of the relationship tables.